Once again, the FDA has issued an approvable letter for Viviant, which would be used to prevent bone loss in post-menopausal women. This is a continued source of frustration for Wyeth, which hopes to combine Viviant with estrogen in a pill called Aprela, which would be used to reduce hot flashes. So, that drug will also remain delayed. The drugmaker had forecast $2 billion in sales for the two drugs.

In its letter, the FDA requested info similar to that outlined in its approvable letter for Viviant’s New Drug Application issued last December, including more analyses about the incidence of stroke and venous thrombotic events, according to Wyeth. And the FDA also identified specific questions concerning data collection, and reporting and requested additional source documents.

The drugmaker, however, downplayed the delay. “Today’s action is in line with our expectations,” Gary Stiles, executive vp and chief medical officer, says in a statement. “In our conference with the agency earlier this year, they stated their desire to convene an advisory committee to review the pending new drug applications for both treatment and prevention of postmenopausal osteoporosis.

This is going to take some, though. Stiles says a complete response will be given to the FDA by the end of the year.